Thing about reflex and quicksilver is that they are so nice for the boss battle that it's a real shame to chug them early. Still, if you can power-level with them, then it's a worthy trade. Try a Warmonger Halfling/Orc Berserker who just drinks every mana potion he finds on the spot sometime. It's a fun little romp.

I will happily trade a Strength + Quicksilver potion for a lvl 4+ kill right out of the gate, but will rarely want to also use the Reflex potion. Quicksilver + Strength lets you get in a single massive strike, but Reflex only adds in your normal strike damage, which is underwhelming at level 1.